Nasal ventilators consist of tubes and other means for delivering gases adapted for use with the nasal or oral passage of a patient. Typically, a nasal ventilator system comprises a gas source, such as a volume ventilator, CPAP system, PIPAP, or IPPB. The gas is most often room air, but can be a mixture of gases. The gas is transported by a thin flexible tube made of an inert material. In a low flow oxygen system, the tube terminates in an opening which can be inserted into the nostril. Typically, the tube splits at a Y-junction into two smaller tubes or a pair of smaller tubes protrude from tube, each smaller tube carrying gas to one nostril via a nasal cannula, thereby increasing the fraction of inspired oxygen.
Conventional nasal ventilation systems use a mask which fits over the nose to deliver a supply of oxygen to the patient. Such systems frequently suffer from air leaking out around the mask, creating an inability to assure ventilation in many patients. Such systems are usually very position dependent, whereby if the mask is moved slightly with respect to the facial contour or with respect to the nose, leakage occurs. As a result many patients lose interest in using the nasal mask. Additionally, with such system, the mask can become uncomfortable when not in position, thus requiring the patient to remain rather still in order to alleviate the discomfort and to maintain oxygen inspiration.
It is important that as much of the gas being transported by the tube reach the lungs of the patient. Conventional tube delivery systems suffer from the disadvantage of not providing a positive seal between the tube and the nostril, resulting in gas leakage around the nasal mask, .which escapes around the mask. It would be desirable for a nasal cannula to form a positive seal within the nostril to pass as much gas as desired to the patient,